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Anatomy Was Groomed. During a Focal Animal Sample 1974). Combining the Three Sampling Procedures A 3 Patterns and Functions of Grooming Behavior among the Common Indian Langur Monkey James J. McKenna For many primate species grooming is a predomin- These data suggest, particularly with respect to the ant and socially important behavior pattern diverse question of functions, that while grooming no doubt both in the form it can take and the social situations serves both social and hygienic functions, it does so in a within which it is initiated. While not the only behavior context apparently dictated -by social needs. It is con- that often cuts across different age and sex classes to cluded that social grooming among langur monkeys is promote cohesion, the tremendous amount of time highly integrated into almost all aspects of group life and energy invested by some species in this activity and, while not a reliable behavioral index to status suggests that as a bond-building mechanism social differentials between group members, it is important grooming has played an auxiliary if not complemen- in assessing role complexes. tary role in the evolution of primate sociality. Among primates social grooming is thought by in- Materials and Methods vestigators to provide useful information on many dif- The study group was housed in a dome-shaped ferent aspects of group life. Grooming data has been mesh enclosure approximately 35 feet high by 45 feet used to measure developmental processes in the in diameter. Starting from the enclosure floor six dif- mother-infant relationship (Hinde 1974, Kaufman ferent levels ofsitting bars and platforms, interspersed and Rosenblum 1969), to document the growing net- every three to five feet, allowed proper social and work of attachments and subgroup formations within spatial refuge. An L-shaped mesh partition support- and among different primate groups (Simonds 1973, ing plywood sitting platforms was situated in the 1974; Furuya 1957; Kummer 1968), and as an exam- center of the enclosure. ple of parental investment (Trivers 1974, Hrdy 1976). According to Jay's (1965) field data, the population While Sade (1965) and Lindberg (1973) demonstrated structure included an adult male (about ten years of how grooming patterns reinforce social relationships age with extracted canines and musculature fully de- and, in some cases, regulate behavior, Chance and veloped); eight adult females (all at least silx years of Jolly (1970) suggested that within private societies the age, primiparous or multiparous); four immature direction of grooming can be used as one criterion to juvenile females (all between the ages of two and four delineate "attention structures" and to assess the de- years of age); four immaturejuvenile males (with mus- gree of social centrality of leader individuals around culature not fully developed and incompletely which others are organized. More recently, Boese erupted canines); and, finally, two dependent infants (1976) used data collected on preferred grooming less than eight months old. clusters to propose that West African baboons (Papio To collect data on the form, frequencies, and dura- papio) exhibit harem units based upon sexual but not tions of behavioral patterns for group members three social exclusivity. different sampling techniques were utilized: focal be- Although an impressive number of works dealing havior samples, focal animal samples, and behavior primarily with the social functions of grooming exist, spot checks. A focal behavior sample involved a fifteen there is not unanimous agreement that grooming be- minute observation period wherein all grooming ac- havior has been interpreted and dealt with correctly, tivities were recorded and notation was made ofwhich nor that its function has been entirely understood. animal initiated the grooming interaction, which other Alexander (1974) argues that not enough attention animal received it, its context, and what part of the has been given to the disease-controlling functions of anatomy was groomed. During a focal animal sample grooming, particularly since grooming may have orig- all behavior exhibited by and toward one individual inally functioned only as a parasite-controlling (the focal animal) during a fifteen minute observation mechanism and not as an accomodation to group liv- period was recorded. The duration of the behavior, ing. To varying degrees Alexander's position receives the actor, the receiver and the participants were noted. support from Hutchins and Barash (1976) and Free- Behavior spot checks involved a random scan and land (1976) who strongly argue that a much closer look periodic survey of the momentary activities of each at the relationship between disease pressures and so- individual at the time of observation (see Altmann cial behavior is warranted. 1974). Combining the three sampling procedures a This paper examines the forms, the contexts, and total of 1500 observation hours were completed. the functions of social grooming behavior among the Tabulation of the data followed the procedure used common Indian langur money (Presbytis entellus). by Lindberg (1973), in which a grooming bout was 4 considered to be any paired occurrence of grooming 60% (n= 1146) classified as relaxed social grooming, involving a recognizable actor and receiver not inter- 4% took the form ofmutual grooming (animal A and B rupted by a third animal or by a major relocation of groom each other simultaneously); 53% involved one of the participants. Reciprocal grooming (animal allo-grooming (animal A grooms animal B); 42% in- A grooms B, then, animal B grooms A) was considered volved reciprocal grooming (animal A grooms animal as two different bouts. If three or more animals B, then, animal B grooms animal A); and, finally, in groomed simultaneously (animal A grooms animal B less than 1% of the relaxed social grooming total the while animal C grooms A), each grooming dyad was form of grooming was unclear, since observation scored separately. If more than ten seconds passed began after the animals had initiated the interaction. between bouts, or it a grooming sequence was termi- Aggressive behavior preceded 63% of tension- nated but begun again after an individual invited a reducing grooming bouts (667 or 35% of all social partner to resume grooming, then this was scored as a grooming bouts observed). Ventral-ventral embracing second grooming bout even though the participants was the second most frequent behavior to precede had previously groomed during the sampling period. tension-reducing grooming with 22% of the total. Sexual solicitations, social mountings, and social pre- Forms of Grooming senting were roughly equal in eliciting grooming re- Although the contexts were varied, three types of sponses (2.5%, 1%, and 4.2% respectively). grooming were recognized for captive Hanuman lan- The third and least frequently observed form of gurs: 1) relaxed social grooming, 2) tension-reducing grooming among captive langurs was self-grooming. grooming, and 3) self-grooming (see table 1). Groom- This form of solitary skin care occurred in 4% of the ing interactions involving more than one animal and total number of grooming behaviors observed. Al- not accompanied by aggressive or tense vocalizations, though spatial and, therefore, social isolation often postures, and/or facial expressions (grimaces) were preceded self-grooming, it was certainly not the only scored as bouts ofrelaxed social grooming. In contrast, condition in which it was initiated. Self-grooming any bout preceded by an embrace, a social present, often occurred between reciprocal grooming sessions aggressive behavior, a social or sexual mount, or a and/or following or preceding allo-grooming by either sexual solicitation involving tense vocalizations and/or one of the participants. facial expressions was scored as a tension-reducing groom. Finally, self-grooming was scored when an in- Frequency and Distribution of Grooming Patterns dividual licked or picked through its own skin, hair, or by Age and Sex Class teeth. Figure 1 shows the percentages by which age and sex classes acted and received Grooming Behavior social grooming (relaxed and tension-reducing grooming combined). Based SOCIAL (96%) SELF (4%) upon 94 fifteen-minute on each of the ____ samples adults RELAXED (60%) TENSION-REDUCING (35%) and immatures (excluding the neonates) and 399 focal la 0 _ behavior hours (1,596 fifteen-minutes observation periods) I found that during any one sample period an average of 3.6 individuals could be found either as - a 0q a<aaa, actors or receivers in grooming interactions. The adult male was involved in more grooming interactions than or A 0~~~j any other individual (331 10% of the total and received approximately twice as much grooming as he returned. a q As an age and sex class the adult females partici- in the actor role more than twice as as a- pated frequently they did in the receiver role (actor to receiver ratio for adult females was 1/2.2). While a t-test comparing the differences between the mean frequency of initiated grooming bouts per animal per class showed that adult females initiated and acted grooming at rates signific- Table 1. Taxonomy of the forms, contexts, and percentages of different grooming behaviors observed among captive Hanuman antly different (p. <01) than either immature males or langurs (P. entellus) females, there is much variation within age and sex classes which deserves attention. When adult females As Table 1 reveals, of the observed 1907 initiated are treated as a class of individuals grouped on the grooming behaviors 60% involved relaxed social basis of age and sex statuses the standard deviation was grooming, 35% involved tension-reducing grooming, 46 and the coefficient of variation was extremely high and 4% involved solitary or self-grooming. Utilizing (21.3). This figure assumes more meaning when it is Sparks (1967) distinctions, I computed that, of the considered that one adult female (Goldie) initiated far 5 time in grooming, males invest little and receive much Ad' A¶? (see Figure 2). 60 I S4 Not only did adult females initiate social grooming 0 more frequently and for longer periods of time, but ; 50 their grooming networks were much more extensive.
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